It's here on page 111 of the Manual:
'About the Lens Correction Data
The camera already contains lens peripheral illumination correction data for approx. 25 lenses. In step 2, if you select [Enable], the peripheral light correction will be applied automatically for any lens whose correction data has been registered in the camera.
With EOS Utility, you can check which lenses have their correction data registered in the camera. You can also register the correction data for unregistered lenses.'
And I had to type that in because Canon have locked the .pdf version of the Manual against copying: 'You cannot edit or copy this document'!